For a guy with one AR that started out as a braced pistol, pulling and tossing the brace is OK per the rule. It does not matter if there are notches or setscrew indents on the buffer tube. Putting a smooth buffer tube on that pistol does not make it any "more legal".
The "Constructive Possession" is all about having parts around (anywhere on a given piece of property or anywhere in your home as I understand it) that can only be used in a wrong configuration.
Going forward, the function of most AR buffer tube and brace assemblies is really no different than most AR rifle buffer tube and stocks assemblies.
For most folks with more than a couple of ARs, the key to a "problem combination" is probably more the pistol length barrels. If you have no pistol length barrels, you are at zero risk. If you do have pistol barrels, but have plenty of AR stuff, just make sure that:
1. You do not assemble a wrong combination.
2. You do not get rid of stuff in sequence that leaves you with only a wrong combination of parts.
A situation I feel is much less common can also be considered. Lets say someone has one or more ARs and only pistol length barrels at a given location. For this case, having either a brace or an AR rifle buttstock at this location meets the ATF description of "Constructive Possession" for an illegal SBR.